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| 4. |
- Almer, J., et al.
(författare)
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Strain and texture analysis of coatings using high-energy x-rays
- 2003
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 94:1, s. 697-702
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the internal strain and crystallographic orientation (texture) in physical-vapor deposited metal nitride coatings of TiN and CrN. A high-energy diffraction technique is presented that uses synchrotron x rays and an area detector, and which allows the strain and intensity distributions of multiple crystallographic planes to be measured by a single x-ray exposure. Unique texture states and nonlinear sin2 strain distributions are observed for all coatings investigated. Quantitative analysis indicates that existing micromechanical models can reasonably predict strain and corresponding stress for mixed-hkl reflections but are inadequate for fully describing measured data. Alternative mechanisms involving deposition-induced defects are proposed
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| 7. |
- Ericsson, Torsten, 1938-, et al.
(författare)
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Studies of residual stress, microcracks, hardness and microstructure of cold compacted metallic green bodies
- 2003
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Ingår i: Materials Research Society Symposium Proceedings. - 0272-9172 .- 1946-4274. ; 759, s. 53-64
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Tidskriftsartikel (refereegranskat)abstract
- The residual stresses have been measured by X-ray and neutron diffraction on PM green bodies manufactured by conventional and high speed compaction of iron powder with and without added copper and brass powder. Compressive residual stresses are present in a thin layer in both top and side surfaces. They are largest in the side surfaces due to plastic deformation of the surface material caused by the friction forces during ejection out of the die. In the interior of the green body residual stresses exist with certain region under compression (periferical regions) and other under tension (more central regions). It is unclear whether mixing iron powder with brass or copper powder leads to considerable phase stresses between the two phases.
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| 10. |
- Gibmeier, Jens, et al.
(författare)
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Residual Stress Distributions around Clinched Joints
- 2002
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Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 404-407, s. 617-622
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Tidskriftsartikel (refereegranskat)abstract
- Clinching is a mechanical press joining method, which has become of growing interest in recent time since it has the potential to replace other conventional joining methods like e.g. spot welding. However, there still exists a lack of knowledge in terms of the mechanical behavior of clinched joints under quasistatic or cyclic loading. For that reason clinching is usually used for applications in structures which are not subjected to external loads. In particular the residual stress distribution in the vicinity of clinched joints and its influence on the mechanical behavior of the joints is unknown. Here diffraction methods are used for the determination of characteristic residual stress distributions in undismantled clinched samples. A combined residual stress determination by X-ray and neutron diffraction has been used to get a well-founded assessment of the residual stress distributions in the immediate vicinity of clinched joints. The residual stress analysis is supplemented by characterizations of the microstructures and the mechanical properties of single clinched joints. Two materials with different strain hardening behavior were used for clinching, a micro alloyed steel (ZStE340) and a non age hardenable aluminum base alloy (AlMg5). In addition two different common clinching techniques were applied - the TOX- [5] and the Eckold-technique [6]. Characteristic residual stress distributions were found for the combinations of clinching techniques and joined sheet materials investigated here. It has been determined that the clinching process induces predominantly compressive residual stresses inside the clinch and in the immediate vicinity of the clinch. The near surface residual stress distributions determined by X-ray diffraction measurements tend to reveal somewhat different residual stresses than measured by neutron diffraction, indicating a possible stress gradient through the sheet thickness. Further evaluation of the FWHM-values of the respective interference profiles shows that for both clinching techniques the largest amount of plastic deformation occurs in the clinch lock region.
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| 11. |
- Gibmeier, Jens, et al.
(författare)
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Residual stress in clinched joints of metals
- 2002
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Ingår i: Applied Physics A. - : Springer. - 0947-8396 .- 1432-0630. ; 74:SUPPL.II, s. s1440-s1442
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Tidskriftsartikel (refereegranskat)abstract
- Diffraction methods are used for the determination of characteristic residual stress (RS) distributions in undismantled clinched samples for the assessment of the influence of RS on the mechanical behaviour of clinched joints. While X-ray diffraction enables merely the determination of near-surface RS distributions, the higher penetration depth of neutron radiation allows the determination of triaxial RS states inside the material. In addition, the complex geometry of clinched joints restricts the application of X-ray RS analysis. Therefore a combined RS determination by X-ray and neutron diffraction has been used to obtain an expressive assessment of the RS distributions in the immediate vicinity of clinched joints. Two different materials with different mechanical behaviour were used for clinching, as well as two different common clinching techniques.
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| 12. |
- Johansson, Sten, 1948-, et al.
(författare)
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Measurement of average texture of cold-rolled aluminium sheet by electron back-scattering diffraction : a comparison with neutron diffraction
- 2001
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Ingår i: Materials Science & Engineering. - 0921-5093 .- 1873-4936. ; 315:1-2, s. 129-135
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of the average texture on sheet of commercial pure aluminium have been performed using neutron diffraction and electron back-scattering diffraction (EBSD). Orientation distribution function maps have been calculated and compared. The results show a good correspondence provided that the data from the EBSD measurements are corrected according to a texture index versus inverted number of measurement procedure. Most errors are probably related to differences in investigated volume and calculation technique and to the fact that the microstructure was difficult for EBSD measurements.
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| 15. |
- Peng, Ru, 1960-, et al.
(författare)
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Characterisation of residual stress distribution in clinching joints of carbon steel by diffraction methods
- 2003
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Ingår i: Materials Science and Technology. - : Informa UK Limited. - 0267-0836 .- 1743-2847. ; 19:3, s. 336-342
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Tidskriftsartikel (refereegranskat)abstract
- Sheet joints of carbon steel fabricated by two different clinching methods, namely TOX and Eckold, have been investigated. The holding force of the joints was determined by shear tension tests and the deformation microstructure was characterised using optical microscopy. The surface residual stress and mean residual stress distributions as a function of increasing distance from the outer diameter of the interlock button were mapped by X-ray and neutron diffractometry, respectively.The Eckold joints showed more severe joint distortion in the form of global sheet bending, but nevertheless possessed higher shear tension strength than the TOX joints. Characteristic residual stress distributions depending on the clinching method were found in both the TOX and Eckold joints. The observed residual stress distributions have been attributed to the different die construction employed by the two methods, which permitted different degrees of plastic deformation during clinching.
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| 17. |
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| 18. |
- Peng, Ru, 1960-, et al.
(författare)
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Intergranular strains and plastic deformation of an austenitic stainless steel
- 2002
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Ingår i: Materials Science & Engineering. - 0921-5093 .- 1873-4936. ; 334:1-2, s. 215-222
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Tidskriftsartikel (refereegranskat)abstract
- Intergranular strains due to tensile plastic deformation were investigated in a sheet material of austenitic stainless steel. The objective was to study the development of residual intergranular strains in samples unloaded from the intermediate and large plastic deformation regimes for which few theoretical and experimental studies were available. By using neutron diffraction, residual lattice strain distribution as a function of sample direction was mapped for a number of crystallographic planes. Deformation microstructures were examined by both transmission electron microscopy and the electron back scattering pattern technique. Residual intergranular strains were observed in samples deformed significantly beyond the elastic limit and the strains varied with sample directions as well as the amount of applied plastic strain. In addition, a different tendency of intergranular strain evolution was observed after large plastic deformation, which could be attributed to the change of dominant plastic deformation mode from slip to mechanical twinning. The results are discussed based on the observed deformation microstructure studies. ⌐ 2002 Elsevier Science B.V. All rights reserved.
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| 23. |
- Schlauer, Christian, 1975-, et al.
(författare)
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Residual Stresses in a Nickel-based Superalloy Introduced by Turning
- 2002
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Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 404-407, s. 173-178, s. 173-178
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Tidskriftsartikel (refereegranskat)abstract
- Near-surface residual stress distributions in the nickel-based superalloy Inconel 718 that originate from the machining operation turning are studied. The turning process that is used in the experiments is face grooving which gives quasi-orthogonal cutting conditions. Cutting speed and feed have been varied to investigate their effects on the residual stress state. Tensile residual stresses with a maximum of 1300 MPa were found at the surface that turn rapidly into compressive residual stresses of up to -800 MPa. The depth distributions of the residual stresses are presented and discussed with respect to observations made by optical and transmission electron microscopy.
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| 24. |
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| 25. |
- Wang, Y D, et al.
(författare)
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Determination of the stress orientation distribution function using pulsed neutron sources
- 2003
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Ingår i: Journal of applied crystallography. - 0021-8898 .- 1600-5767. ; 36:1, s. 14-22
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Tidskriftsartikel (refereegranskat)abstract
- The stress orientation distribution function (SODF) was recently introduced as a mean-field representation to describe the grain- orientation dependence of intergranular stress. Pulsed neutron sources are ideally suited for the determination of the SODF since multiple reflections can be measured simultaneously with comparable precision. A method is developed for constructing the SODF from strain pole figures measured with a pulsed neutron source and demonstrated with cold-rolled interstitial-free steel. The experimental results are compared with those measured with a reactor-based constant-wavelength diffractometer. It is shown that access to a large number of reflections on a pulsed neutron source improves the precision of the experimental SODF and facilitates in situ studies of the evolution of the intergranular stress during deformation and annealing.
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| 26. |
- Wang, Y D, et al.
(författare)
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Grain-orientation-dependent residual stress and the effect of annealing in cold-rolled stainless steel
- 2002
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Ingår i: Acta Materialia. - 1359-6454 .- 1873-2453. ; 50:7, s. 1717-1734
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Tidskriftsartikel (refereegranskat)abstract
- Cold rolling leads to a residual stress that is dependent not only on the specimen directions but also on the orientation of the grain. Neutron diffraction was used to investigate residual stresses and the effect of annealing in cold-rolled stainless steel, a two-phase material consisting of 62 vol% austenite and the rest deformation-induced martensite. The specimens were prepared by cold rolling of AISI 301 stainless steel with 48% reduction. The grain-orientation-dependent residual stress, or inter-granular stress, was determined by constructing the stress orientation distribution function, a recently developed concept, from the residual strains measured along various crystallographic directions. For the cold-rolled sample, a strong grain orientation anisotropy was observed for residual stresses in both phases. Detailed analysis of the experimental stress and texture data indicates that the observed orientation anisotropy was caused by the selective phase transformation that occurred during cold rolling. Annealing at 500░C leads to recovery, which significantly reduces the orientation anisotropy of the residual stress. The experimental data show that the recovery dynamics in the austenite and martensite phases are quite different. It appears that the overall recovery behavior in this two-phase material is driven by the martensite phase. ⌐ 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
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| 27. |
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| 28. |
- Wang, YD, et al.
(författare)
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Stress-orientation distribution function (SODF) - Description, symmetry and determination
- 2000
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Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 347-3, s. 66-71
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a stress-orientation distribution function (SODF) is defined to describe statistically the distribution of the stress state of grains as a function of crystal orientation. Similar to the crystal orientation distribution function (CODF), the SODF may be expressed as generalized spherical harmonics. The two symmetry groups existing in the SODF, namely the crystal symmetry and the sample symmetry, are discussed. A method to construct the SODF directly from neutron or X-ray diffraction data is described, Finally, the validity of the method is demonstrated by stress analysis of simulated strain distributions in an austenitic stainless steel under tensile loading.
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